body {
    font-family: Arial, sans-serif;
    margin: 20px;
    background-color: #f0f0f0;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    background-color: white;
    padding: 20px;
    border: 2px solid #666;
}

h1 {
    text-align: center;
    color: #333;
    margin-bottom: 30px;
}

.panels {
    display: flex;
    gap: 20px;
}

.panel {
    flex: 1;
    border: 2px solid #999;
    padding: 20px;
    background-color: #fafafa;
}

.panel h2 {
    margin-top: 0;
    color: #444;
    border-bottom: 1px solid #ccc;
    padding-bottom: 10px;
    margin-bottom: 20px;
}

textarea {
    width: 100%;
    box-sizing: border-box;
    font-family: monospace;
    font-size: 12px;
    border: 1px solid #999;
    padding: 10px;
    margin-bottom: 10px;
    resize: vertical;
}

input[type="password"] {
    width: 100%;
    box-sizing: border-box;
    font-family: monospace;
    font-size: 12px;
    border: 1px solid #999;
    padding: 10px;
    margin-bottom: 15px;
}

.key-input {
    height: 120px;
}

.message-input {
    height: 100px;
}

.output-area {
    height: 150px;
    background-color: #f9f9f9;
}

button {
    background-color: #ddd;
    border: 2px outset #ddd;
    padding: 10px 16px;
    font-size: 14px;
    cursor: pointer;
    margin-bottom: 15px;
}

button:hover {
    background-color: #ccc;
}

button:active {
    border: 2px inset #ddd;
}

.copy-button {
    padding: 5px 10px;
    font-size: 12px;
    margin-left: 10px;
    margin-bottom: 5px;
}

.error {
    color: red;
    background-color: #ffe6e6;
    border: 1px solid red;
    padding: 10px;
    margin-top: 10px;
    border-radius: 4px;
}

.success {
    color: green;
    background-color: #e6ffe6;
    border: 1px solid green;
    padding: 10px;
    margin-top: 10px;
    border-radius: 4px;
}

label {
    font-weight: bold;
    display: block;
    margin-top: 15px;
    margin-bottom: 5px;
    color: #444;
}

.footer {
    text-align: center;
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid #ccc;
    color: #666;
    font-size: 12px;
}

@media (max-width: 768px) {
    .panels {
        flex-direction: column;
    }
    
    .container {
        margin: 10px;
        padding: 15px;
    }
}